Catalytic oxidation of naphthenes



Patented Nov. 1938 UNITED STATES caranmc oxma'non or NAPHTHENES Nicholas a. Mila's, Belmont, Mass., and wiuiam L. Walsh, East Greenbush, N. Y., assignors to Research Corporation, New York, N. 1., a corporation of New York Application August 28, 1937,, Serial No. 161,528

' no Drawing.

7 Claims. (Cl. 260-451) This invention relates tothe controlled catalytic oxidation of naphthene hydrocarbons to the production of maleic acid or its anhydride, and otheruseful products.

In processes embodying the catalytic oxidation of organic compounds it is the usual, if not the invariable, practice flrstto vaporize the base compound and then pass a mixture of the vaporized compound and an oxygen containing gas into lO contact with a suitable cataly'zer maintained at a temperature of from 350 to 600 C.,thereby effecting a vapor phase reaction. The contact time in all 'such processes is necessarily low,

usually of the order of 0.3 second or less,.and'

the yields of-the more valuable products, such as maleic acid, are in many cases quite unsatisfactory, particularly where the base compound is of a highly volatile character.

Moreover, as catalytic oxidation; are highly exothermic and-as the reaction is carried out wholly in the vapor phase, there is present. at all dangerin'g the safety of the'operator. Hence, it

so heretofore has been the usual practice to employ for the catalytic oxidation special means for maintaining the base compounds in vapor phase.

I and special means for dissipating excess heat or for maintaining the reaction chamber atatemperature within a predetermined range.

It is an object of the present invention to 7 provide an improved process for effecting the catalytic oxidation of naphthenic compounds if 40 petroleums, by which process the aforeme itioned objectionable features inherent in the prior ;art catalytic oxidation processes are avoided."

Another object of the invention is the provision of a process for the catalytic oxidation of naphf thenic-petroleums not involving the employment of extraneous heat other thani'or maintaining 1 j the catalyst at the desired temperature. Other objects include the provision of a process for catalytically oxidizing naphthenesto maleic acid Land/or maleic anhydride'characteriaedby easy maintenance of a substantially constant temperature equilibrium; to provide a process, of. the type'aforesaid, which promotes oxidation without first having to vaporize the petroleum and then contact the vapor with the. heated catalyst! and to provide catalytic oxidation of naphthenic petroleum, at the'minimum temperatureconsistent with satisfactory yield of the desired oxidation'product. R

These, and other, objects of invention are realized by the carrying out of the process according to which the naphthenic petroleum material to be oxidized if normally a liquid, is first passed through a stream of oxygen (or oxygen-contain- 5 ing gas) and is broken up to form a heavy spray so that each liquid particle may adsorb, entrap or otherwise annex asmuch oxygen as possible without effecting any appreciable vaporization of the compound; but where the compoundis normally a solid, it is first prepared in a powder or granular form and then .passed through a stream or atmosphere of oxygen in the form ofadispersion of discrete particles, in both cases the initial step being carried out at normal temperature (20 to 25C.). The liquid or solid dispersion is then brought into direct contact with a suitable catalyzer which is maintained at, the optimum'temper ature conditions for the particular compound and V in an atmosphere containing oxygen in an amount ten to thirty times the'theoretical equivalent-of that necessary for complete oxidation.

The naphthenic material at the time of initial contactwith the catalyzer immediately" goes apartial oxidation whichgenerates I preciable amount of heat, which heat to raise the temperature of the oncoming. unoxi- I dized material. V

The depthof oatalyzer and rate of flow or feeding of the reaction mixture" is such that a contact period of between 1 and 6 seconds (pref-' erably approximating 1.5 seconds) is maintained. By applying the minimum amount of heat necessary to maintain the catalyzer at its proper temperatureand by uniformly conducting the. reaction mixture through the reaction zone, a

' substantially constant temperature equilibrium within the reaction zone may be established and maintained, thereby avoidingexcessive temperatures and their attendant dangers and eliminating the necessity of using apparatus embodying cooling coils or expensive high temperature bath,

such as mercury'and molten, sulphur, in orderto dissipate the heat of the reaction.

The catalyst may comprise a compound containing one or more or the elements of the fifth or sixth groups of the periodic system, for ex- V ample, gvanadium, bismuth, molybdenum, tungsten, etc., which compounds may preferably form a coating on a carrier such as pumice, Alundum", asbestos, fullers earth, kieselguhr, or the v like material.-

A specific catalyst composition found to be operable for the satisfactory carrying out of the aforesaid process is that produced by precipitating vanadium pentoxideor a mixture of vanadium pentoxide and molybdenum oxide-on v pumice, as is described in greater detail .in apso plication Serial No. 38,050, filed August 27, 1935, for Catalytic oxidation of organic compounds". By the carrying out of the process aforesaid upon naphthenic petroleum material there is.

produced a reaction mixture containing useful products including carboxylic acids, the chiefuseful oxidation products being maleic acid and its anhydride.

found to be operable using, crude natural Mid- Continent petroleums, and fractions thereof.

from the Oklahoma and Texas (Winkler) fields.

and also naphthene-containing petroleums from Louisianan, Mexican, Venezuelan, Roumanian and Russian fields, and also the waxes derived wax and then catalytically oxidize the vapor.

from the oil deposits of the fields just mentioned.

The 'operability of waxes marks the unique adapnext to impossible) first to vaporize a petroleum While the. invention is not restricted to the use of a particular and specific apparatus, it is preferred to use for the purpose the catalytic oxidation apparatus more-specifically described in application Serial No. 38,050, filed August 27,

1935, for Catalytic oxidation of organic compounds, which apparatus, in essence, comprises; an enclosed reaction chamber; a bed in the-lower part of saidchamber and containing a mass of the catalytic material; means for maintainchamber for conducting a current of gas and a nique and catalytic procedure are given dispersionof the material'to be oxidized downwardly wherebythe. latter is brought into contact with the catalyst mass while in its original phase.

Illustrative oithe process of the present invention the following specific data of experi-'- jments carrying out the above-described tech- Tntx 1 Oklahoma crude l m0 (in 1 I seconds) of mum Pueeut yield temp. oi oimsleioloid oxidation elyst male '0. Crude oil (not purified) 410 1.0 Over 10 Various fractions of crude I oil identified by boiling pointrango: 1 34-350 0. (sulphur v I 1 3: 380-4 10 '1 o izs-i-z' rimso' a m c. nest s hurproducts 380-410 1.0 14-10 78-1 0. (free from sulphurproducts) 380-410 0. 8 13-14. 5 78-150 0. (free irom snlphurmoducts)" 321-410 1:0 15-21 78-150 0.0;

, 811$!!! products). 321-410 2. 4 13-18. 6 34-1 0; (free in sulphur pmdlwtl)" 470 0.4 6, 34-100 0. (free from sulphur products)- 470-61 0. 8 11-. ii 34-1 0. (ii-cc I sulphur products)- 410 1.! I 18 34-100 0. (tree from sulp wpmduchi)" 410 2.4 11- 78-150 a and rccir- 41. I 1.6 $.5-

In all cases in which two optimum temperatures' were given above, the lowerjt'emperature corresponds tov the loweryield recorded in the last column." The oxidation of both'types of petroleum I was studied also at temperatures above as well as below the limits given inthe.

foregoing tables;- as a'result of these researches,

it was found that operation at the above "optimum temperatures of oxidation .gave superior yields of maleic acid (and/or its anhydride) as opposed to operation atlesser or greater temperatures,- other conditions being constant.

It will be appreciated that the above recited experiments were conducted on a laboratory scale. From the experience gained in thecarrylog out of the process of application Serial No. 38,050 both on laboratory scale and on a. largermore-nearly commercial"scale, it has been found generally that yields of larger scale'operations are 'higher than for the corresponding laboratory scale. I Accordingly, it may reasonably be assumedthat larger scale operation-of the' instant process will'be attended by higheryields than the already satisfactory'ylelds stated in Tables I and 11 above. 'I'his invention'. therefore common'with, application Serial No. 38,050.

We claim:

" 1; Processwhich forming a nongaseous dispersion of a liquid to solid naphthenic hydrocarbon in finely divided non-gaseous form inan atmosphere containing free oxygen, at

normal'rocm temperature; conveying said nongaseous dispersion to a'catalyst containing a compoundof an element'of the'fifth and sixth groups of the periodic system and being maintained at a temperature between and 500 1 0.. whereby-there is produced a reaction mix ture containing asubstantial amount of a maleic acid compound; and withdrawing the, reaction mixture from contact with the catalyst.

2. Process which comprises forming a nongaseous dispersion of a liquid to solid naphthenic hydrocarbon infinely divided non-gaseous form in an atmosphere containing free oxygen, at nor- I of a maleic I acid compound; and withdrawing the reaction gaseous dispersion of a liquid to solid naphthenic hydrocarbon in finely divided non-gaseous form in an atmosphere containing free oxygen, at normal room temperature; conveying said non gaseous dispersion to a catalyst containing a compound of an element of the fifth and sixth groups of the periodic system and being main tained at a temperature between 300 and 500 0., contact with the catalyst being maintained for at least one second and not to exceed about six seconds, whereby there is produced a raction mixture containing a substantial amount of a maleicacid compound; and withdrawing the reaction mixture from contact with the catalyst.

4. Process as defined in claim 1, characterized in that after the reaction mixture is withdrawn from contact with the catalyst maleic acid compound is. recovered from .the mixture and the residual mixture is recirculated over the catalyst.

5. yrccess as defined in claim 1, characterized in that a petroleum mixture containing a naphthene hydrocarbon is the material dispersed.

6. Process as defined in claim 1, characterized in that there is used as the material dispersed a fraction oi naphthenic petroleum freed from sulphur compounds.

7. As a new product, a mixture of petroleum hydrocarbons and oxidized derivatives thereof including a substantial content of a maleic acid compound.

- NICHOLAS A. MILAB.

WILLIAM L. WALSH. 

